Kaposi sarcoma-associated herpesvirus (KSHV) ORF57 is a multifunctional, nuclear protein involved in post-transcriptional regulation of a subset of viral genes during lytic replication. Three nuclear localization signals (NLSs), NLS1 (amino acids (aa 101-107), NLS2 (aa 121-130), and NLS3 (aa 143-152), were identified in the N terminus of the ORF57 protein, and each of the three represents a short stretch of basic amino acid residues. Disruption of all three NLSs prevented localization of ORF57 in the nucleus. Insertion of individual NLSs into a heterologous cytoplasmic protein converted it into a nuclear protein, confirming that each NLS functions independently and is sufficient to promote protein nuclear localization. Although it exhibits a function similar to that of Epstein-Barr virus EB2 in promoting KSHV ORF59 expression, KSHV ORF57 differs from the herpes simplex virus ICP27 protein, and its function could be disrupted by point mutations of single or two NLSs in random combination, despite the proper localization of the mutant protein in the nucleus. The dysfunctional ORF57 containing NLS mutations also had low affinity with ORF59 RNA and the RNA export factor REF. However, the REF binding of ORF57 in vivo appeared to have no effect on ORF57-mediated enhancement of ORF59 expression. Thus, the three NLSs identified in ORF57 provide at least two functions, nuclear localization of ORF57 and up-regulation of ORF59 expression.

Interleukin (IL)-23 is an essential cytokine involved in expansion of the Th17 lineage, which is associated with many immune-related destructive tissue diseases. We hypothesized that the IL-23-induced Th17 pathway plays a role in periodontal pathology and examined the expression of cytokines, and related molecules, in periodontal lesions and control sites. IL-23 and IL-12 were expressed at significantly higher levels in periodontal lesions than in control sites. However, the relative expression of the IL-23 receptor compared with the IL-12 receptor beta2 was significantly higher in periodontal lesions. Moreover, IL-17 expression was significantly higher in periodontal lesions, especially in the tissue adjacent to bone destruction, than in control sites. There was no significant difference in the expression levels of IFN-gamma, an important cytokine inhibiting differentiation toward the Th17 pathway, between periodontal lesions and control sites. Together, these results suggest that the IL-23-induced Th17 pathway is stimulated in inflammatory periodontal lesions.